1. Field of the Invention
This invention relates to a video data recording and reproducing apparatus, a video data reproducing apparatus with data modification detection, and a method of recording and reproducing video data with data modification detection.
2. Description of the Prior Art
A video data recording and reproducing apparatus for recording video data and reproducing the video data, a video data reproducing apparatus for reproducing video signal, and a method of recording and reproducing video data are known.
FIG. 13 is a block diagram of a prior art video data recording and reproducing apparatus. A video signal from a camera 101 is a/d-converted into video data by an a/d converter 104. The video data is compressed by a video data compression circuit 105 and recorded on a recording unit 106. A video data expansion circuit 107 expands the video data from the recording unit 106. A d/a converter 108 d/a-converts the video data from the video data expansion circuit 107 into a reproduction video signal. The reproduction video signal is displayed on a display monitor 103. When there is a request for modifying the video data or editing the video data, a password processing circuit 109 identifies the inputted password. If the inputted password is correct, it is allowed to modify or edit the video data.
The aim of the present invention is to provide a superior video data recording and reproducing apparatus, a superior video data reproducing apparatus, and a superior method of recording and reproducing video data.
According to the present invention there is provided a first video data recording and reproducing apparatus. In the first video data recording and reproducing apparatus, a data compression circuit compresses video data. A first modification detection data generation circuit generates first modification detection data in accordance with the compressed video data. A combining circuit combines the video data with the first modification detection data to output combined data. A recording circuit records the combined data on a recording medium. A reading circuit reads the combined data from the recording medium. A separating circuit separates the combined data from the reading circuit into the compressed video data and the first modification detection data. A second modification detection data generation circuit generates second modification detection data in accordance with the compressed data from the separating circuit. A comparing circuit compares the data modification detection data from the separating circuit with the second data modification detection data. A data expansion circuit expands the compressed video data from the separating circuit to output expanded video data. An outputting control circuit controls outputting the expanded video data in accordance with the result of the comparing circuit.
In the first video data recording and reproducing apparatus, the first modification detection circuit may include an error check code generating circuit for generating the first modification detection data from at least a portion of the video data and the first modification detection circuit may generate the first modification detection data from at least a portion of the video data. The first modification detection data is represented with one selected from the group consisting of check sum codes, parity codes, and Cyclic Redundancy Check codes.
The first video data recording and reproducing apparatus may further include a recording circuit for recording the combined data from the reading circuit on a removable recording medium.
According to the present invention there is also provided a first video data reproducing apparatus for reproducing combined data including compressed video data and first modification detection data on a removable recording medium, the video data being recorded with first modification detection data generated in accordance with the video data with correspondence with the video data. In the first video data reproducing apparatus, a reading circuit reads the combined data from the removable recording medium. A separating circuit separates the combined data from the reading circuit into the compressed video data and the first modification detection data. A modification detection data generation circuit generates second modification detection data in accordance with the compressed data from the separating circuit. A comparing circuit compares the first modification detection data from the separating circuit with the second data modification detection data. A data expansion circuit expands the compressed video data from the separating circuit to output expanded video data. An outputting control circuit controls outputting the expanded video data in accordance with the result of the comparing circuit.
In the first video data reproducing apparatus, the reading circuit may include a DVD-RAM drive unit and the removal recording medium comprises a DVD-RAM disc.
In the first video data reproducing apparatus, the modification detection data generation circuit may include a first software processing circuit for executing a first program to generate the second modification detection data. The comparing circuit may include a second software for comparing the data modification detection data from the separating circuit with the second data modification detection data. The data expansion circuit may include a third software for expanding the compressed video data from the separating circuit.
In the first video data reproducing apparatus may further include: a time data generation circuit for generating present time data; a condition detection circuit including a memory and an input circuit for detecting a condition in accordance with condition data from the memory and input data from the input circuit; an electronic watermark data adding circuit for generating watermark data from the present time data and the condition and adding the watermark data to the expanded video data to generate watermark data added video data; and a recording circuit for recording the watermark data added video data on another removable recording medium.
The first video data recording and reproducing apparatus may further include: a network interface circuit for communicating with a network; a decrypting control data generation circuit for generating decrypting control data in accordance with an encrypting key; an encrypting circuit for encrypting the combined data with the encrypting key. The network interface circuit may transmit the encrypted combined data and the decrypting control data to the network.
According to the present invention there Is further provided a second video data reproducing apparatus for reproducing data encrypted with a first key from a network. In the second video data reproducing apparatus, a network interface circuit receives video data and decrypting key data generated from the first key from the network. A decrypting key data generation circuit generates a second key in accordance with the decrypting key data. A decrypting circuit decrypts the data with the second key. A recording circuit in the second video data reproducing apparatus records the decrypted data on another removable recording medium.
According to the present invention there is further provided a second video data recording and reproducing apparatus. In the second video data recording and reproducing apparatus. A data compression circuit compresses video data. An encrypting circuit encrypts the video data from the data compression circuit with a first key. A recording circuit records the video data from the encrypting circuit on a recording medium. A reading circuit reads the video data from the recording medium. A storing circuit stores the first key. An inputting circuit inputs a second key. A decrypting circuit decrypts the video data from the reading circuit with the second key. A data expansion circuit expands the video data from the decrypting circuit to output expanded video data. When the first key corresponds to the second key, the video data is correctly decrypted.
In the second video data recording and reproducing apparatus, the first key may be a common encrypting key.
The second video data recording and reproducing apparatus may further include an encrypting key encrypting circuit for encrypting the first key with one selected from a group including a common encrypting key or a public encrypting key.
The second video data recording and reproducing apparatus may further include: a key encrypting circuit for encrypting the first key in accordance with key data; a combining circuit for combining the video data from the encrypting circuit with the first key from the key encrypting circuit to output combined data; a recording circuit for recording the combined data on a removable recording medium.
According to the present invention there is further provided a third video data reproducing apparatus for reproducing data including encrypted compression video data and a key used for encrypting the data. The key is encrypted with first key data. In the third video data reproducing apparatus, a reading circuit reads the data on a removable recording medium. A separating circuit separates the data from the reading circuit into the encrypted compression video data and the key. An inputting circuit inputs second key data. A key decrypting circuit decrypts the key with the second key data. A data decrypting circuit decrypts the compression video data from the separating circuit with the key from the key decrypting circuit. An expansion circuit expands the compression video data from the data decrypting circuit to output expanded video data.
The second video data recording and reproducing apparatus may further include: a network interface circuit for communicating with a network; an enciphering key control circuit for receiving key data regarding the first key from the network and enciphering the first key in accordance with the key data. The network interface circuit transmits the video data from the reading circuit and the enciphered first key to the network.
According to the present invention there is further provided a fourth video data reproducing apparatus for reproducing encrypted compression video data. In the fourth video data reproducing apparatus, a network interface circuit receives the encrypted compression video data and a key used for encrypting compression video data. The key is encrypted with first key data. An inputting circuit inputs second key data. A key decrypting circuit decrypts the key with the second key data. A data decrypting circuit decrypts the compression video data from the network interface circuit with the key from the key decrypting circuit. An expansion circuit expands the compression video data from the data decrypting circuit to output expanded video data.
According to the present invention, there is a first method of recording and reproducing video data with data modification detection including the steps of: generating first modification detection data in accordance with the compressed video data; correspondingly recording the compressed video data and the modification detection data on a recording medium; reading the compressed video data and the first modification detection data from the recording medium; generating second data modification detection data in accordance with the read compressed data; comparing the read first data modification detection data with the second data modification detection data; and controlling reproducing the compressed data in accordance with the comparing result.
According to the present invention, there is a second method of recording and reproducing video data with data modification detection including the steps of: generating an encrypting key every file of the video data; encrypting a file of the video data with the enciphering key; recording the file on a recording medium; reading the file on the recording medium; inputting circuit for inputting a second key; decrypting the video data with the second key. Thus, the decrypted video data can be used when the first key corresponds to the second key.
According to the present invention there is further provided a third video data recording and reproducing apparatus. In the third video data recording and reproducing apparatus, a first modification detection data generation circuit generates first modification detection data from video data. A recording circuit correspondingly records the video data and the first modification detection data on a recording medium. A reading circuit reads the video data and the first modification detection data from the recording medium. A second modification detection data generation circuit generates second modification detection data in accordance with the video data from the reading circuit. A comparing circuit compares the first data modification detection data from the reading circuit with the second data modification detection data. An outputting control circuit controls outputting the video data from the reading circuit in accordance with the result of the comparing circuit.
The third video data recording and reproducing apparatus may further include: a data compression circuit for compressing video data to supply compressed video data to the first modification detection data generation circuit and the recording circuit as the video data; and a data expansion circuit for expanding the video data from the reading circuit to supply expanded video data to the outputting control circuit as the video data.
According to this invention, there is provided a fifth video data reproducing apparatus. In the fifth video data reproducing apparatus, a receiving circuit receives video data and first modification detection data generated in accordance with the video data. A modification detection data generation circuit generates second modification detection data in accordance with the video data from the receiving circuit. A comparing circuit compares the first modification detection data from the receiving circuit with the second data modification detection data. An outputting control circuit controls outputting the video data in accordance with the result of the comparing circuit.